VANADIUM-CONTAINING NASICON MATERIALS

Abstract: The present invention provides a composition of matter having the formula: AxB1-xVyC1-yP3O10-15 wherein A is Nb or Ta, B is Sb or As, C is Ti, Zr, Sn, or Ge, and 0 </= x </= 1, 0 < y </= 1; a composition of matter having the formula: MzAxB1-xVyC1-yP3010-15 wherein M is selected from the group consisting of Cu, Ag, Na, K, and Cs, A is Nb or Ta, B is Sb, C is Ti or Sn, and 0 </= x, y, z </= 1; and a composition of matter having the formula: MzAxB1-xVyC1-yP3-nSin010-15 wherein M is selected from the group consisting of Cu, Ag, Bi, Na, K, Rb, and Cs, A is Nb or Ta, B is Sb or As, C is Ti, Zr, Sn, or Ge, and 0 </= x, z </= 1, 0 < y </= 1, and 0 </= n </= 2. Such compositions are useful as, for example, catalysts for the selective oxidation of hydrocarbon feedstocks.

Description: VANADIϋM-CONTAINING NASICON MATERIALS This invention relates to a vanadium (IV)-containing composition of matter having the structure of a NASICON (Sodium (Na) Super Ionic Conductor) material and to the use of such a material in upgrading organic feedstocks. The NASICON structure has been reported to consist of a three-dimensional framework built up from PO. tetrahedra and MO,, octahedra, where M is a metal ion which has been incorporated into the NASICON framework. The PO. and MO- tetrahedra are believed to share vertices to form secondary building units of the general formula M 2 (P0.) 3 . These building units are reported to be stacked along the c-axis to form fairly large cavities that are interlinked to form tunnels. These tunnels are believed to contain sodium. The NASICON phases initially attracted attention because of the high mobility of Na+ ions in the tunnels of the parent phase Na.Zr.Si PO.., giving rise to high ionic conductivity and use in fuel cells [see P. Hagenmuller and . Van Gool Solid Electrolytes Academic Press, New York (1978)]. The stability of the NASICON framework and its ability to form solid solutions containing a wide variety of elements has also been exploited in the preparation of zero thermal expansion coefficient (ZTEC) materials (see A. El Jazouli et al. C.R.Acad.Sc.Paris t.300, Serie II, n° 11, 1985, 493-496). More recently, the isostructural phases with copper substituted for sodium have been reported to be catalytically active for the decomposition of alcohols (see A. Serghini et al., J. Chem. Soc, Faraday Trans., 1991, 87, 2487-2491). For a discussion of the synthesis of vanadium- containing NASICON materials, see A. Bermoussa et al., Journal of Solid State Chemistry 97, 314-318 (1992), and J. Gopalakrishnan et al., Chemistry of Materials, Vol. 4, No. 4, 745-747 (July/August 1992). The present invention provides a composition of matter having a NASICON structure and the formula: A χ B l-x V y C l -y P 3°10-15 wherein A is Nb or Ta, B is Sb or As, C is Ti, Zr, Sn, or Ge, and O ≤ x ≤ l, 0 < y < 1. The invention further provides a composition of matter having a NASICON structure and the formula: M z A x B ι-x v y c ι-y P 3 °ιo-i 5 wherein M is selected from the group consisting of Cu, Ag, Bi, Na, K, Rb, and Cs, A is Nb or Ta, B is Sb, C is Ti or Sn, and 0 < x, z ≤ l, 0 < y < 1. The invention still further provides a composition of matter having a NASICON structure and the formula: M z A x B l-x V y C l-y P 3-n Si n°10-15 wherein M is selected from the group consisting of Cu, Ag, Bi, Na, K, Rb, and Cs, A is Nb or Ta, B is Sb or As, C is Ti, Zr, Sn, or Ge, and 0 < x, z ≤ l, 0 < y < 1, and 0 < n < 2. The material of this invention is a useful catalyst for upgrading organic feedstocks. The material promotes partial oxidation reactions, such as the reaction of n-C. to form products less deeply oxidized than CO and CO- (such as maleic anhydride, furan, and butadiene) . The material also catalyzes the reaction of alkylaromatics, e.g., o- xylene, to aromatic oxygenates e.g., phthalic anhydride. Phthalic anhydride can be used in preparing alkyl, amino, and epoxy resins, as a flame retardant, rubber retarded, or as an ester for plasticizers and polyesters. When calcined at at least 700 β C, niobium-containing materials of the invention (e.g., NbVP-O.-) may be characterized by their x-ray diffraction pattern, which includes the d-spacings shown below in Table 1. After calcination at 700 β C or above, the antimony- containing materials of the invention (e.g., SbVP.O.-) may be characterized by their x-ray diffraction pattern, which includes the d-spacings shown in Table 2. Table 2 After calcination at 700°C or above, the antimony- and titanium-containing materials of the invention (e.g., SbTi. 5 V Q 5 *P 3 0 12 ) ma Y be characterized by their x-ray diffraction pattern, which includes the d-spacings shown in Table 3. Table 3 These X-ray diffraction data were collected with a Scintag diffraction system, equipped with a germanium solid state detector, using copper K-alpha radiation (λ=l.541780) . The diffraction data were recorded by step- scanning at 0.04 degrees of two-theta, where theta is the Bragg angle, and a counting time of 10 seconds for each step. The interplanar spacings, d , s, were calculated in Angstrom units (A) , and the relative intensities of the lines, I/I_ is one-hundredth of the intensity of the strongest line, above background, were derived with the use of a profile fitting routine (or second derivative algorithm) . The intensities are uncorrected for Lorentz and polarization effects. The relative intensities are given in terms of the symbols vs = very strong (60-100) , s = strong (40-60) , m = medium (20-40) and w = weak (0-20) . It should be understood that diffraction data listed for this sample as single lines may consist of multiple overlapping lines which under certain conditions, such as differences in crystallographic changes, may appear as resolved or partially resolved lines. Typically, crystallographic changes can include minor changes in unit cell parameters and/or a change in crystal symmetry, without a change in the structure. These minor effects, including changes in relative intensities, can also occur as a result of differences in cation content, framework composition, nature and degree of pore filling, and thermal and/or hydrothermal history. The material of this invention is useful as a catalyst for upgrading organic feedstocks and is particularly effective for selectively oxidizing a hydrocarbon feed. Such oxidation reactions include the conversion of n-butane to maleic anhydride and the conversion of o-xylene to phathalic anhydride. These reactions are suitably carried out in the presence of oxygen under conversion conditions including temperature of 100 to 500 β C, preferably 200 to 350"C, a pressure of 100 to 800 kPa (0 to 100 psig) , and an LHSV typically of 0.1 to 20, preferably 0.2 to 5.0. The ratio of oxygen to hydrocarbon typically ranges from 5 to 20. When used as catalyst, the composition of the invention may be incorporated with another material which is resistant to the temperatures and other conditions employed in the catalytic process. Such materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and/or metal oxides such as alumina. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Use of a catalytically active material may change the conversion and/or selectivity of the catalyst. Inactive materials suitably serve as diluents to control the amount of conversion so that products can be obtained economically and orderly without employing other means for controlling the rate of reaction. The composition of the invention may also be combined with clays, e.g., bentonite and kaolin, which serve as binders to improve the crush strength of the catalyst under commercial operating conditions. Naturally occurring clays which can be used include the montmorillonite and kaolin family, which families include the subbentonites, and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite, or anauxite. Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification. Useful binder materials also include inorganic oxides, notably alumina. In addition to the foregoing materials, the composition of the invention can be composited with a porous matrix material such as silica-alumina, silica- magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as ternary compositions such as silica-alu ina-thoria, silica-alumina-zirconia, silica- alu ina-magnesia and silica-magnesia-zirconia. The relative proportions of the composition of the invention and inorganic oxide matrix may vary widely, with the content of the material of the invention ranging from 1 to 90% by weight and more usually, particularly when the composite is prepared in the form of beads, in the range of 2 to 80% weight of the composite. The invention will now be more particularly be described in the Examples and the accompanying drawings, in which: Figure 1 compares n-butane conversion (y-axis, weight percent) as a function of temperature (x-axis, * C) in the presence of oxygen and two catalyst compositions of the invention. The open circles represent data for conversion in the presence of a material of the invention having the formula NbV 0 . 5 Ti 0 . 5 P 3 O x which has been heated to a temperature of about 450 * C. The solid circles represent data for conversions in the presence of a material having the formula NbV 0>5 Ti 0 . 5 P 3 O x which has been heated to a temperature of at least 700 * C. Figure 2 compares the yield of maleic anhydride from n-butane conversion (y-axis, weight percent) as a function of temperature (x-axis, * C) in the presence of oxygen and two catalyst compositions of the invention. The open circles represent data for conversion in the presence of a material of the invention having the formula NbV 0 . 5 Ti 0 . 5 P 3 O x which has been heated to a temperature of about 450'C. The solid circles represent data for conversions in the presence of a material having the formula NbV 0 . 5 Ti 0 . 5 P 3 O x which has been heated to a temperature of at least 700 * C. Examples Starting Materials Columbium oxalate (Nb(HC_0.) 5 ) was obtained from Atomergic Chemetals Corp. Ammonium vanadate (NH.V0_) , antimony(III) oxide (Sb_0-), diammonium hydrogen phosphate (NH 4 ) 2 HP0 4 ), oxalic acid (H 2 C 2 0 4 ) , and citric acid (H g C 6 0 7 ) were obtained from Aldrich Chemical Co. Example 1 - Preparation of NbVP o I. The following three solutions were prepared: SI: NH 4 VO 3 (3.0g, 0.0256 mil) + H 2 C 2 0 4 .2H 2 0 (7.0g, 0.053 mil) + H 2 0 (lOOmL). The color changed to deep blue in less than 1 hour, indicative of the formation of VO 2+. The solution was heated and stirred for a further 60 hours. Si: Nb(HC 2 0 4 ) 5 (13.77g, 0.0256 mil) + H^O .2H 0 (7.0g, 0.053 mil) + H O (350 mL) . The solution was slightly turbid even after heating for 60 hours. S3: (NH 4 ) 2 HP0 4 (10.16g, 0.077 mil) + H 2 0 (100 L) . SI was added to S2 and then S3 was added to the mixture. The slightly turbid blue solution was allowed to dry completely on a hot-plate and the residue was collected, ground, placed in a fused quartz crucible and heated under a nitrogen atmosphere to 600°C and 3°C in " . The temperature was held constant for 10 hours and allowed to return to ambient. The green powder was reground and heated to 600°C under nitrogen atmosphere at 25 β C min-1 and held at that temperature for 15 hours. The green product exhibited a featureless x-ray diffraction pattern. The green powder was then reheated to 900 β C under nitrogen atmosphere and held at that temperature for 40 hours. II. A mixture containing NH 4 VO_(6.0g, 0.0512mil), Nb(HC 2 0 4 ) 5 (27.54g, 0.0512 mil), oxalic acid (5g) and citric acid (5g) was dissolved in H 2 0 (200 mL) . A slightly turbid deep blue solution was obtained on heating and stirring. When (NH.J-HPO. (20.32g, 0.1536 mil) was added to this solution a light blue precipitate was immediately formed. This was collected after the water had been completely evaporated, ground, placed in a fused quartz crucible and heated to 450"C at 3"C min~ under nitrogen atmosphere and held at that temperature for 10 hours. After the 450"C heating step, the material exhibited a featureless x-ray diffraction pattern. Product samples were allowed to cool to room temperature, ground, mixed with oxalic acid (2.0g) and reheated to 700 * C, 800 * C, and 900°C at 25°C rnin "1 and held at that temperature for 50 hours. Tables 4, 5, and 6 shows the x-ray diffraction patterns of this material after heating. Table 4 Table 5 10 15 Table 6 10 15 20 25 2θ range = 2.0 - 52.0" Step size = 0.04 λ = 1.541780 Automatic baseline correction 11 point bimodal smoothing I. A (11.7g, 0.1 mol) and (NH 4 ) 2 HP0 4 (39.6g, 0.3 mol) was ground, placed in a fused quartz crucible and heated at 3°C min~ to 500°C in air. The temperature was held constant for 50 hours and the product cooled to ambient temperature. This was ground finely, reheated to 750 β C in air and held for 10 hours, this was repeated one more time. II. A mixture of Sb 0 (14.5g, 0.05 mil), NH VO (11.7g, 0.1 mil) and (NH 4 ) 2 HP0 4 (39.6g, 0.3 mil) was ground, placed in a fused quartz crucible and heated to 450°C at 1°C min~ and held at that temperature for 10 hours in air. The green powder was allowed to cool to ambient temperature, ground and reheated to 750°C at 25°C min " and held at that temperature for 15 hours. This was repeated one more time with a 40 hours annealing time. Table 2 shows the x-ray diffraction pattern of this material. Example 3 ; Preparation of SbTi Q V 5 -5 3 -2U 2 A mixture of Sb 2 0 3 (4.3g, 0.0147 moϊ) ~ , NH 4 VO ~ (1.73g, 0.0147 mol), Ti 2 (C 2 0 4 ) 3 . 10H 2 O (4.0g, 0.0074 mol) and (NH.) HPO. (11.73 molg, 0.0888 mol) was ground and heated to 450"C at 3"C mm . -1 and held at that temperature for 10 hours in air. The yellow brown powder was heated to 750°C at 25 β C min " and held for 12 hours. The green brown powder was ground and reheated to 800°C and held for 15 hours. Table 3 shows the x-ray diffraction pattern of this material. Example 4; Conversion of n-Butane to Maleic Anhydride The materials of Example 1 were evaluated for selective oxidation activity and selectivity using a n- butane feed. The performance of the x-ray amorphous material of Example 1 (which had been heated to a temperature no higher than 450 * C) was compared with that of the crystalline material which had been heated to a temperature of at least 700'C. Results are plotted in Figures 1 and 2, and show that heating the material to a temperature of at least about 700'C improves its activity and selectivity for converting n-butane to maleic anhydride.

Claims: Claims: 1. A composition of matter having the formula A x B ι-x v y c ι-y P 3 °ιo-i 5 wherein A is Nb or Ta, B is Sb or As, C is Ti, Zr, Sn, or Ge, and O ≤ x ≤ l, 0 < y < 1. 2. The composition of claim 1 further characterized by the x-ray diffraction pattern of Table 1. 3. The composition of claim 1 further characterized by the x-ray diffraction pattern of Table 2. 4. The composition of claim 1 further characterized by the x-ray diffraction pattern of Table 3. 5. A composition of matter having the formula M z A x B l -x V y C l -y P 3 °1 0 -15 wherein M is selected from the group consisting of Cu, Ag, Bi, Na, K, Rb, and Cs, A is Nb or Ta, B is Sb, C is Ti or Sn, and 0 < x, z ≤ l, 0 < y < 1. 6. A composition of matter having the formula M z A x B l-x V y C l-y P 3-n Si n°10-15 wherein M is selected from the group consisting of Cu, Ag, Bi, Na, K, Rb, and Cs, A is Nb or Ta, B is Sb or As, C is Ti, Zr, Sn, or Ge, and 0 ≤ x, z ≤ l, 0 < y ≤ 1, and 0 < n < 2. 7. The composition of any preceding claim which has been calcined at a temperature of at least 700°C. 8. A process for upgrading a hydrocarbon feedstock comprising partially oxidizing said feedstock in the presence of the composition of as claimed in any preceding claim.

Inventors: AGASKAR PRADYOT ADWAITANAND, GRASSELLI ROBERT KARL, AGASKAR, PRADYOT, ADWAITANAND, GRASSELLI, ROBERT, KARL
Applicants: MOBIL OIL CORP, MOBIL OIL CORPORATION
Application year: 1994
Main classification: B01J27
IPC codes: B01J27, C01B25, C01B33, C07D307